Hi Peter, there's one detail about the use of these verbs that kind of sets them apart. In contexts like the one you posted, SER is used to make a broad generality - something so obvious that you're speaking for everyone: the cake was beautiful (nobody would deny it). However, ESTAR is used to express one's own reaction - what tastes good to you may not taste good to someone else. Also, ESTAR is used to refer to a specific thing, whereas SER is, again, used for generalities: El caviar es delicioso - is something you would say if you were speaking generally about caviar; El caviar está delicioso - if you were giving your personal opinion about a specific caviar, say at a party. Hope this helps - let me know if you have any questions.